1. Technical Field
The present invention relates to a stamper for forming a fine pattern or a structure on a substrate. It also relates to a transfer apparatus using the stamper.
2. Background Art
FIG. 3 schematically illustrates the process of forming a mask pattern on a thin film provided on a substrate by applying an organic resin to the substrate and then molding the organic resin with a stamper. A stamper 104 is moved over a substrate 101 on which a thin film 103 and an organic resin layer 102 have been formed, while pressing evenly the stamper onto the organic resin layer 102 that has not been cured, thereby transferring a pattern formed on the stamper onto the organic resin layer 102. After the transfer of the pattern, the organic resin layer 102 is heated or irradiated with light so as to cure the organic resin layer 102 and thus fix its shape, thereby forming a mask pattern 105 to be used as a protective mask for etching. Using this mask pattern 105, the thin film 103 is etched such that the thin film is removed except where the film is masked by the mask pattern 105, thereby pattering the thin film (see JP Patent Publication (Kokai) No. 5-80530 A (1993) (par. 0023 to 0028 and FIG. 1), for example).
As a method of allowing only the concave-convex pattern on the surface of the stamper to be transferred in spite of irregularities in the thickness of the stamper or bulges on the back surface of the stamper, the following is known. FIG. 4 shows a process of transferring the shape of the stamper to a photosensitive resin 112 by pressing a base plate 111 onto the resin 112. Behind the stamper 113 are disposed a member 117, a two-sided adhesive tape 116, a resilient member 115 and a vinyl sheet 114. Thus, any irregularities in the thickness of the stamper 113 or bulges on the back surface of the stamper can be absorbed by the resilient member 115 disposed behind the stamper (see JP Patent Publication (Kokai) No. 5-73968 A (1993) (par. 0011 and FIG. 1), for example).
Of the aforementioned conventional techniques, the one illustrated in FIG. 3, whereby the pattern is transferred to the resin on the silicon substrate, employs a rigid body made of a light-transmitting organic resin or glass as the stamper. The surface of the stamper or the silicon substrate has height irregularities on the order of several micrometers. These height irregularities pose an obstacle in accurately transferring fine structures on the order of micrometers or less.
This problem can be overcome by producing the stamper with a flexible material such that the stamper can accommodate the contour of the substrate. However, in order to allow such a flexible stamper to follow the contour of the substrate accurately, a buffer must be disposed on the back surface of the stamper. As such a buffer, the resilient member that is used in the other conventional technique, namely the transfer process illustrated in FIG. 4, could be used.
When the flexible stamper is pressed onto the resin on the substrate, the areas on the surface of the stamper that have many convex portions come into contact with the resin first. As a result, these areas receive a larger resistance from the resin than other areas on the stamper surface and are warped, such that the pattern on the stamper surface cannot be correctly transferred to the resin. Such unevenness in the transfer cannot be solved by the use of the resilient member in the transfer process for photosensitive resin as shown in FIG. 4, whereby force is applied to the entire surface of the stamper in an equal manner.
It is therefore the object of the invention to provide a stamper capable of accurately transferring the pattern on the stamper to a transferred item without being influenced by the distribution of the convex portions on the stamper surface or irregularities of the substrate, a transfer apparatus that utilizes such stamper.